Various electronic devices such as a smart phone, tablet personal computer (PC), portable multimedia player (PMP), personal digital assistant (PDA), laptop PC, and wearable device have become popular.
Recently, various electronic devices are being equipped with a port for connecting an external electronic device in a wired system. Various standards define the port, and one of the most widely used standards is a universal serial bus (USB) type.
The USB is an input/output standard widely used for connecting an electronic device and an external electronic device.